Large solar energetic particles (SEP) events, especially those that produce widespread particle intensity increase and ground level enhancements, pose significant radiation hazards to the inner heliosphere. Over the past several decades, our knowledge about energetic particle acceleration, propagation, and distribution in the large SEP events has significantly increased, with a number of important processes identified. However, it has been difficult to isolate and distinguish different mechanisms and evaluate their relative effects. Both Parker Solar Probe and Solar Orbiter, among other remote sensing and in situ observations, are currently providing unprecedented coverage in the inner heliosphere. Meanwhile, new insights have been obtained from analytical theory, plasma kinetic simulations and models that bridge different scales and make predictions for realistic events. We invite observers, modelers, and theorists to jointly solve the mysteries in large SEP events. Efforts that bridge observations, theory, and predictive models are particularly encouraged.